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Records of 46 patients with classic phenylketonuria (PKU) were used to determine treatment variables associated with intellectual outcome. Patients comprised three groups: phenylalanine-restricted diet started 1) after 3 months and loss of diet control at a mean age of 7 years, 2) before age 3 months and loss of diet control at a mean age of 5 years, and 3) before age 3 months and through a mean age of 11 years. All underwent IQ testing during the diet; groups 1 and 2 were retested at a mean of six years off the diet. On the diet, groups 2 and 3 had higher IQs than group 1; group 3 IQ was also higher than IQ off diet in groups 1 and 2. After discontinuing the diet, group 2 IQs decreased significantly. Predictors of IQ in group 1 were age at loss of diet control and percentage of phenylalanine concentrations >15 mg/dL; in group 2, mean phenylalanine concentrations and age at loss of diet control. Predictors of changes in group 1 IQs were global degree of dietary control and percentage of phenylalanine concentrations >15 mg/dL; in group 2, phenylalanine concentrations of 15 mg/dL achieved no IQ gain by continuing the diet after age 7 years. Thus, intellectual prognosis is best for PKU patients who start a phenylalanine-restricted diet early and continue through age 12 years.

The administration of l -leucine to leucine-sensitive children produces profound hypoglycemia. The effect of l -leucine on the blood glucose concentration of normal individuals has been studied. A small but definite effect has been found which suggests that a homeostatic relationship between the amino acid and insulin exists. This relationship is abnormal in the children with leucine-sensitive hypoglycemia.

THE relationship which exists between the thyroid and pituitary has been known for a long time. Thyrotropin (TSH) production is activated in states of decreased thyroid hormone production, and anterior pituitary production of thyrotropin is inhibited by the thyroid hormone secreted. Exogenous thyroid hormone, likewise, inhibits the production of thyrotropin, resulting in decreased synthesis of endogenous thyroid hormone (1). Thus, a reciprocal relationship exists between the anterior pituitary and the thyroid gland. However, most concepts of this interaction are based on morphologic studies or, at best, on indirect physiologic evidence. There have been relatively few measurements of the levels of circulating thyrotropic hormone in humans. In 1951, D'Angelo, Paschkis, Gordon and Cantarow (2) reported observations on the thyroid-thyrotropic hormone balance of normal and endocrinopathic individuals. Data were presented on 9 adults and 1 child with hypothyroidism. The titers of thyrotropin varied widely from ...